This invention relates to indwelling ureteral stents or drainage tubes for use in bypassing urinary tract obstructions or maintaining the patency of urinary passageways. In particular, the present invention addresses an apparatus for use in the placement of ureteral stents in a patient, whether by antegrade or retrograde placement.
Indwelling ureteral stents have been widely used for the past ten years. These stents are placed in the ureter, which is the duct between the kidney and the bladder, for the express purpose of establishing and/or maintaining an open, patent flow of urine from the kidney to the bladder. The predominant indications for placing a ureteral stent include extrinsic compression occlusions, ureteral injury due to trauma, and obstructive uropathy. The typical ureteral stent can be composed of various radiopaque polymers, including polyethylene, silicone, polyurethane, and thermoplastic elastomer. These stents are retained in the ureter by a retentive curve shape, such as a pigtail, coil, J-shape or hook configuration, at either end of the stent that engages the walls of the bladder and the kidney, respectively The stent is resilient to allow it to be straightened for insertion into a body passageway, and still return to its predetermined retentive curve shape when in situ.
Indwelling ureteral stents are positioned in the ureter by antegrade (percutaneous) placement, retrograde (cystoscopic) placement through the urethra, as well as by open ureterotomy or surgical placement in the ureter by direct manipulative control. Ureteral stent positioning has heretofore been accomplished by two basic methods. In one method, a wire guide is introduced into the ureteral orifice in the bladder via a cystourethroscope under direct vision. The wire guide is advanced up the ureter until the advancing flexible tip of the guide is confirmed by X ray or fluoroscopy to be in the renal pelvis of the kidney. A tubular stent with both ends open is fed onto the exposed external segment of the wire guide and advanced over the wire guide by hand until a short segment of the stent is visible outside the cystoscope. A pusher catheter, "positioner" or length of tubing is then fed onto the exposed external end of the wire guide and advanced over the wire guide by hand until it butts against the stent. With the wire guide held stationary, the positioner is advanced over the wire guide to push the tubular stent up the ureter to the renal pelvis. With the anatomically proximal end of the stent in the renal pelvis, the positioner is held stationary while the wire guide is gradually extracted from the stent and the positioner. As the wire guide leaves the proximal end of the tubular stent, the retentive hook or curve of the proximal end of the stent is formed to retain the stent in the pelvis of the kidney. As the wire guide is withdrawn past the distal, or intravesicle, end of the stent, the retentive hook or curve of the distal end is formed so that the stent end is retained within the bladder. At this point, the positioner and wire guide are completely withdrawn leaving only the stent indwelling in the ureter, bladder and kidney.
In another method of ureteral stent placement, a ureteral stent having one end closed is backloaded onto a wire guide. In this "push-up" method, the tip of the wire guide contacts the closed end of the ureteral stent, which is then introduced into the ureteral orifice in the bladder via a cystourethroscope under direct vision. The stent is advanced up the ureter under fluoroscopic control until the tip of the stent lies within the renal pelvis. A positioner catheter or length of tubing is fed onto the external end of the wire guide and advanced over the wire guide by hand until it butts against the open, distal end of the stent. The positioner is held steady while the wire guide is removed in a fashion similar to that described above.
In the first placement method discussed above, the urinary tract is subject to essentially three invasive entries--once when the wire guide is introduced into the ureteral orifice, again when the tubular stent is advanced over the wire guide, and yet again when the pusher catheter is fed onto the wire guide. In the second "push up" placement method, two invasive entries are required--once when the stent and wire guide is inserted, and again when the positioner is fed along the external end of the wire guide. Moreover, in the second method of placement, a closed end stent is required to be pushed by the end of the wire guide. In this respect, the first method of placement is desirable over the "push up" placement method because a tubular stent may be used that is cheaper and easier to produce, and that provides a more open flowpath from the kidney to the bladder through the open ends of the stent.
In view of the limitations of the prior art ureteral stents and placement methods, it is desirable to provide a indwelling ureteral stent kit that requires only a single invasive entry into the ureteral orifice and ureter, while allowing the use of an open ended tubular stent.